This invention relates to a device for movably suspending a working cage in which a workman can work on an outer wall surface of a building and, more particularly, to a device which is particularly suitable for suspending a working cage which is suspended from a roof car which runs along rails aid along the periphery of a roof of a building.
Known in the art is a device for suspending a working cage for performing work on an outer wall surface of a building which, as shown in FIG. 7, includes an arm c secured to a roof car b which can run along rails a laid along the periphery of a roof of a building and one or two swivel arms d which are mounted rotatably horizontally to the under surface of the forward end portion of the arm c. In this prior art device, wire ropes f for suspending a working cage e are secured at one end thereof to a winding device g disposed in the roof car b and, at the other end thereof, to the working cage e. For example, as shown in FIG. 8, wire ropes f consisting typically of two wire ropes f1 and f2 which extend horizontally through the inside space of the arm c are tuned in the vertical direction by a sheave h mounted to the forward end portion of the arm c in such a manner that the sheave h can rotate in a vertical place and extend vertically through a swivel mechanism I for rotating the swivel arm d horizontally. The wire ropes f are then turned in the horizontal direction by sheaves j and k mounted to the swivel arm d at locations below the sheave h in such a manner that they can rotate in a vertical plane. The wire ropes f extend horizontally through a space inside the swivel arm d, are turned again in the vertical direction by sheaves l and m mounted to the ends of the swivel arm d and extend to the working cage e.
In the prior art device shown in FIGS. 7 and 8, the swivel arm d is disposed below the arm c but there is also a prior art device in which the swivel arm d is disposed above the arm c.
When work is performed on the wall surface by the working cage e of the prior art device shown in FIGS. 7 and 8, the winding device g is operated to unwind the wire ropes f from the winding device g or wind them into the winding device g and thereby lower or lift the working cage e.
The prior art device has the advantage that work is facilitated by rotating the swivel arm d when work is performed along a corner portion of a building.
The prior art device for suspending a working cage has however the disadvantage that, when the swivel arm d is rotated by a desired angle by driving the swivel mechanism i, the sections of the two wire ropes f1 and f2 extending in the vertical direction, i.e., the sections between the sheave h and the sheaves k, j, are twisted to twine about each other and, since the wire ropes f1 and f2 are wound or unwound by the winding device g in this entwined state, friction occurs between the wire ropes f1 and f2 with resulting wear and short life of the wire ropes f1 and f2. For this reason, wire ropes must be frequently replaced in this type of device which is disadvantageous both in working efficiency and maintenance and other costs.
Particularly, in a case where a working cage is suspended at four corners of its top surface by four wire ropes through a single arm, friction caused by entwining of four wire ropes in the vertical section is much stronger than in the case of using two wire ropes and, therefore, it has been considered almost impossible to realize suspension of a working cage by four wire ropes through a single arm and, in practice, suspension of a working cage by four wire ropes is effected by using a device having two arms, each arm dealing with two wire ropes. This device using two arms however requires a very complex construction and a troublesome operation because the two arms need to be actuated synchronously in operation.
It is, therefore, an object of the invention to provide a device for suspending a working cage capable of prolonging the life of wire ropes by preventing occurrence of friction caused by entwining of the wire ropes and thereby improving working efficiency and reducing costs.